(i) Field of the Invention
The present invention relates to a catalyst combustor in which a gas or liquid fuel such as kerosine or gas oil is burnt in the presence of a combustion catalyst, and more specifically, it relates to a catalyst combustor which can be suitably used for the combustion of a heat source for driving, for example, an air conditioner.
(ii) Description of the Related Art
According to a catalyst combustor in which a fuel gas such as a hydrocarbon and air are brought into contact with a heated catalyst to achieve combustion without flame, extremely small amounts of CO, HC (hydrocarbon) and the like are exhausted and any flame is not present. Therefore, the formation of nitrogen oxides which nowadays cause a social problem is largely inhibited advantageously. In order to stably carry out the catalyst combustion, the preheating of the catalyst and air to be fed is necessary. For the preheating, there are a method of using an electrical heater or a burner, a method of using a heat exchanger, and the like. When the electrical heater is used for the preheating of air even after the start of the catalyst combustion, a large amount of electric power is consumed, and therefore the use of the electrical heater in livelihood is expensive. In addition, when air is preheated by the burner, the formation of the nitrogen oxides cannot be inhibited, so that the large advantage which the catalyst combustor has is impaired. In order to solve these problems, after the start of the catalyst combustion, it is most effective and economical that a part of the heat of a combustion gas is fed to air for combustion by the use of a heat exchanger to preheat the air for combustion.
In one example of conventional catalyst combustors, a discharge passage for the combustion gas is provided adjacent to the inner wall or the outer wall of a passage of air for combustion to carry out heat exchange, thereby preheating the air for combustion. However, this heat exchange is poor in efficiency, and for the sake of the sufficient heat exchange, it is necessary to sufficiently expand the contact range of both the passages, which inconveniently makes the device large. As another example, there is a method of using a rotary regenerative type heat exchanger. In this method, there is a fear that the combustion gas is mixed with the air for combustion, and driving members for the rotation are additionally required, which inconveniently makes the device large.